Word for low level noise among restless crowd, as sign of confusion or complaint? [closed]

Dictionary gives me "drone" and "murmur" but I'm not sure if that's the word I am thinking of. I want to use it to describe a group of people on strike who hear that their demands are not met and the CEO has resigned. They're not shouting, but they're not whispering either. They're restless and confused. I want to say that a certain something (murmur?) was heard among the crowds, to indicate their state.

I think you were spot on with murmur as suggested in the question:

A low continuous background noise:
‘the distant murmur of traffic’

(Oxford Dictionaries)

A more relevant example could be:

The murmuring crowd was distracting the speaker.

Or, as a noun:

A murmur of agreement spread through the crowd at the suggestion.

"a rumbling of discontent" may work.

Rumbling: synonym of rumble:

• a deep, heavy, somewhat muffled, continuous sound
• a widespread murmur of discontent

Discontent:

• dissatisfaction

The word you're looking for is mutter. The Oxford Living Dictionary has, as a noun:

A barely audible utterance, especially one expressing dissatisfaction or irritation.

And as an example for the verb:

Back-benchers were muttering about the next reshuffle.

I asked an online thesaurus for synonyms of clamor. Perhaps one of these would suit for the murmuring crowd:

• buzz
• brouhaha
• hubbub

There was a [buzz/brouhaha/hubbub] as the CEO's resignation was announced.